B737 flight crew reported a loss of aircraft control while in a holding pattern due to experiencing turbulence and heavy rain when flying into a cloud.
Synopsis
B737 flight crew reported a loss of aircraft control while in a holding pattern due to experiencing turbulence and heavy rain when flying into a cloud.
Narrative
We were on the ZZZZZ arrival when ATC notified us to hold as published at ZZZZZ1 at FL190. Once established in the hold; we began to notice that the leg distance was too close to weather; so we made the decision to shorten the holding leg in order to avoid the weather in the area.As we shortened the hold; we encountered a cloud that initially did not appear significant to any of the three pilots accompanying the flight deck or on the radar return. However; once inside the cloud; we experienced heavy rainfall and turbulence; which resulted in an upset condition. The aircraft annunciated 'ROLL MODE.'Recognizing the upset; first officer called out 'UPSET;' the Autopilot had automatically disconnected and he manually disconnected the autothrottle; and proceeded with the upset recovery procedure; verbalizing each step aloud. The aircraft descended approximately 300 feet from our assigned holding altitude during recovery. Recovery within a few seconds back to altitude assigned and lateral track were achieved.We promptly informed Approach Control of the situation and the in-flight conditions. Due to the strong winds pushing the storm into the protected area of the hold; we requested and were provided with an alternate route. The flight continued and was completed without incident.
Second reporter narrative
We were in the ZZZZZ arrival when ATC notified us to hold as published at ZZZZZ1 at FL190 feet. Once established in the hold; we began to notice that the leg was too close to the storm; so we made the decision to shorten the holding leg in order to avoid the thunderstorm in the area.As we shortened the hold; we encountered a cloud that initially did not appear to be significant to either the Captain or myself. However; once inside the cloud; we experienced heavy rainfall and turbulence; which resulted in an upset condition. The aircraft annunciated 'ROLL MODE'.Recognizing the upset; I immediately called out 'UPSET'; and I disconnected the Autopilot and auto throttle; and proceeded with the upset recovery procedure; verbalizing each step out-load. We descended approximately 300-400 feet from our assigned altitude during recovery.We promptly informed Approach Control of the situation and the inflight conditions. Due to the strong winds; pushing the storm into the protected area of the hold; we requested and we were provided with an alternate route.After all; we landed safely; we did our parking checklist and the Captain and I debriefed.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.